UDP Protocol Reference
Reference for UDP: datagrams, ports, checksums, and use cases for connectionless transport.
Protocol Characteristics
UDP (User Datagram Protocol, RFC 768) provides connectionless, unreliable datagram delivery. Each datagram is independent; there is no connection setup or teardown. The 8-byte header contains source/destination ports, length, and checksum. UDP does not guarantee delivery, ordering, or duplicate detection. The minimal overhead makes it suitable for latency-sensitive and broadcast/multicast traffic. Applications must handle reliability if needed.
- connectionless
- No handshake
- unreliable
- No delivery guarantee
- header
- 8 bytes
statelessbest effortports + checksumUse Cases
DNS uses UDP for queries due to low overhead and fast responses. Real-time media (VoIP, video) tolerates packet loss better than delay, favoring UDP. QUIC builds reliable transport over UDP. Multicast and broadcast require UDP (TCP is point-to-point only). Online games use UDP for real-time state updates. Application-level reliability (FEC, retransmission) can be added where needed. UDP-Lite allows partial checksums for error-tolerant media.
- DNS
- Low overhead queries
- real-time
- VoIP, video
- multicast
- One-to-many
falls back to TCPloss > delayTCP cannot